Class D Technology

Whatever Ralph meant the mid-fi comment did make me laugh knowing that the sound I hear from practical Class D amps today (like the ones I own which are neither the least or most expensive) is not mid-fi by any reasonable listening standard.

@mapman  Do you think that because we've taken this technology very seriously that at the same time we don't?

If I can point out some things without people trying to put words in my mouth, first- tube amps are rarely mid-fi. The term 'Mid-fi' refers to equipment generally sold in box stores like Best Buy (not including their in-store Magnolia dealerships); stamped out to make money. Tube amps are usually too expensive for that (tube power is generally expensive, which is why there were many high efficiency speakers on the market when tubes were the only game in town decades ago).

The thing about most solid state is that the specs really haven't changed a whole lot since the late 70s or early 80s. Like I said, compare a Kenwood amplifier a Krell and you will see what I mean. The big difference is power (on paper). Bandwidth and distortion are almost the same. Of course a Krell is built better, has bigger heatsinks and bigger power supplies. And its not sold in box stores.

Class D has almost entirely taken over at the bottom end of the audio market. And the middle part too. You can't buy a boom box now days that isn't class D. For the number of class D amps in total on the market, only a tiny minority (the ones that generally have our attention) are considered high end. Many of them use the same modules found in mid fi gear.

Think about that for a moment before railing on me? I'm only working with the facts here so don't shoot the messenger. If you look at a high end tube amp or a traditional solid state amp, **NONE** of them use parts/circuitry/assemblies also found in mid fi gear.  This is something different about class D and has entirely to do with how inexpensive the technology actually is.

(To give you an idea of that, I have a module on my desk that was sent to me by a customer (who happens to be the vice president of Phillips Semiconductor). This was one of their best modules built about 12-13 years ago. It makes 100 watts per channel and is a stereo module that is complete except for the power supply. It even has connectors on the board for easy hookup. The specs are quite good (Phillips TDA8920B, scans at 317KHz!; not bad for decade-old technology; faster than some amps made today and features no 'dead time') and it sounds alright too. In quantities of 1 it cost $25.00. I know of at least one 'high end' amp that uses this module that cost $2500.00. This module is the size of a pack of cigarettes complete with connectors and heatsink.)

So when I talk about mid fi and class D, you **should** know why now. I think a lot of posters here are attaching a negative meaning to the 'mid fi' term that does not exist; Just because its mid fi does not mean it has to sound bad and I can point to plenty of examples (we could start with the Radio Shack Lineaum speakers). What I'm seeing in class D is something I've not seen in audio before- amplifiers that use the same parts as a mid fi amp as in a high end amp. In fact its safe to say that class D has lifted mid fi performance to what many would have called 'high end' only a decade earlier.

So you might like your amp and I'm not disputing that! OK, I'll say it again, you might like your amp and I'm not disputing that. But if you think that the amp does not share a lot with mid fi gear you are ***really*** mistaken.

There is one other thing that keeps getting left out of this discussion. Its a simple fact that no matter what the amp is, if you make it work hard for a living its not going to sound as good because its distortion will be higher. This is easy to hear and easy to measure!! You can see it in the specs of any amp. Tube amps in general are best experienced when driving higher impedances 8 ohms or more. All output transformers are more efficient driving higher impedances and also will have wider bandwidth (its not unusual for an output transformer to loose an octave of low frequency bandwidth going from the 4 ohm tap as opposed to the 8 ohm tap). For this simple reason, Magnaplanars and Ohm Walsh loudspeakers are not the best candidates to really tell how good a tube amp actually is (the tube amp will sound better on a load that's easier to drive, and so will any solid state amp). My speakers at home and here at the shop are both 16 ohms and very different designs; both extremely transparent. When both amps are on a level playing field their differences are more easily assessed.

At any rate, if you are happy with what you hear than that's really what's important. If you have audiophile nervosa, which is a deadly disease (I've had it for decades and its no picnic) you are always left wondering what's around the next bend, how you can arrange things to get better sound. I've outlined already how class D has to improve (FWIW, some of the complaints I have apply to regular amps as well), which we hope to address in our design.

Mid fi has a negative connotation in these parts. That’s all. One can either laugh or be insulted. Best to not use the term unless that is the message intended.

Some amps of any type can be labeled as mid fi compared to others of same type, SS Class D, tube, whatever based on whatever criteria one chooses including the sound quality.

The point is not all of any type are created equal. Some of each type these days compete in the big leagues but play the game differently. Some in the minor leagues.

Also safe to say Class D competes well in all leagues at most any price point these days.

Its generalizing and labeling all products of a particular type equally for better or for worse that causes problems just like labeling all persons of a particular nationality or religion negatively causes similar confusion and problems, just of a lesser importance in the case of hifis.

The BelCanto C5i in particular has shocked me in that my quite tube amp friendly Triangle Titus speakers sound the best ever with it. The 60 w/ch are Ok but not the best with any of my OHM or Dynaudio speakers though I have had visitors from Agon still compliment the sound with those even. Which just goes to show it all depends. Class D amps play the game radically different than OTL tube amps do. But both can deliver big league results (Class D for less perhaps especially when cost of speakers factored in) based on my listening experience perhaps both even with easier load speakers that are required more for the OTL or tube amps but easier load in general tends to benefit all amps to some extent when done right.

Also I would note that modern OHM Walsh speakers (especially the larger models) are a good bit more efficient than Magnepans and not as tube amp unfriendly as one might anticipate. I found Magnepan to need power (though not so much current) to a much greater degree than OHM when I owned both.

Why do the people who say they don't like class D mention the class D amps they have heard?  One guy slammed the H2o's that he had obviously never even heard.....how ridiculous is that?!  No not all class D amps are great but there are plenty that are EVERY BIT AS GOOD (and better) than any other design.

I had a Bel Canto Class D amp a few years ago and it was awful. However, I heard the Channel Islands Audio Class D mono block amps a while ago at an audio show and judged them to be outstanding.  Class D amp technology has progressed and I don't doubt it will be the wave of the future for audiophiles.  

I had the Ice Amp 125ASX2 and it was awful.